Automatic telephone exchange



April 1,1924; 1,488,691-

F. A. LUNDQUIST AUTOMATIC TELEPHONE EXCHANGE ginal Filed 1917 23% 70356 I Si April 1, 1924. 4

eat 2 Original Flled Sept. 15,

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T0 HENRY S. CONRAD, TRUSTEE.

AUTOIL'A'TTC TELETPHONE EXCHANGE.

"Substitute for application Serial r 2.919, Serial No. 305

To all whom 2'5 may concern:

Be it known that T, Team; A. LUND- outer, a citizen of the United States of America, and a resident of the city of Chi cago, county of Cook, and State of Tllinois, have invented certain new and useful limprovements in Automatic Telephone Exchanges, of which the following is specification.

My invention relates to automatic telephone exchanges, and has for its object an improved arrangement of trunk connections which will bring about a reduction in the number of such trunks and the amount of apparatus required to equip'an exchange.

This application is a substitute for my former application, Serial No. 1591,5 12, filed Sept. 15, 1917.

In ordinary exchanges, a trunk selecting switch has its wipers normally located near, or moved to, a group of contact terminals. In selecting a trunk, these wipers are automatically advanced over the terminals of this group until they reach terminals which represent an idle trunk. Vihcn this point reached the switch is automatically stopped with its wipers in engagement with the found trunk, which trunk is automatially made busy so that it will not be contlictingly selected by some other switch moving its wipers over otherterminals of the same trunk.

The trunk thus automatically selected loads to another switch which, in turn, selects an idle trunk leading to still another switch. The number of such automatic selections in making a call is determined by the size of the exchange, the last automatic selection being of a trunk leading to a connector switch. The connector switch has its n'iovements controlled by the subscriber malz ing the call, and connects to terminals oi lines leading to the local stations of subscribers.

The first trunk-selecting switches in an exchange are usually called line switches and are connected to the lines leading to the local stations. There is thus one line switch for each subscriber. The line switches usually have terminals for from ten to twenty trunks leading to selectors, which are the switches between the line switches and the connectors. The selectors usually have ter- To. 131,542, filed September 15, 1.917.

This application filed June 20,

540. Renewed January 26, 1922. Serial No. 532,038.

minals for one hundred trunks, arranged in ten groups of ten trunks in each group. The subscriber selects the desired group, but the selector automatically selects an idle trunk out of the previously selected group.

The line switches and the selectors of the present exchange are assumed to be the same as those in ordinary use, or to be any switches which will accomplish the same result. The connectors, however, are assumed to have terminals for one thousand lines leading to local stations. T have described such a switch in my pending application Serial Number 186,448, filed August 16, 1917, issued as Patent No. 1,455,497, Nov. 27, 1923.

The actual construction of none of these switches is, however, material to the present application, as this application relates solely to the trunking and grouping organization used.

The switches in an organization are arranged in groups, and the number of trunks leading to the switches of a particular group is determined by the size of the group and the trafiic conditions. When the groups consist or one hundred switches each, normal trafiic conditions require about fourteen trunks to serve them. It is known, however, that by making the groups larger, at less percentage of trunks is necessary to serve them. Thus, in groups of one thousand, fifty trunks, or five per cent of trunking, is suiiicient. The object here is to obtain the advantage of large groups without making large and cumbersome switches... In other words, to obtain large groups while using standard switches now' employed 111 small groups of one hundred or less.

The accompanying drawing represents, on three sheets, a part of an organization serving one hundred thousand subscribers. The sheets are extensions of each other, Sheet To. 1 being at the left, Sheet No. 2 next, and Sheet No. 3 at the right. The three sheets together represent the first one thousand line switches, and eight hundred out of the second one thousand. The line switches are represented at A in a row at the bottom of the three sheets. The first selectors are rep resented at B in the next row above the line switches. Similarly, the second selectors are represented at G, and the connectors at D. In this or anization the one hundred thousand capacity is reached without the use of third selectors.

Each switch is represented by a single contact maker, or wiper, 10, 11, 12, 13, or arbitrarily by the circles in a line with the lower endsof the wipers. A cable 14 having wires for one thousand lines extends along below the line switch A, which wires terminate each in a different wiper 10. Four wipers 10 are arbitrarily used to represent a sub-group of one hundred line switches, and the cable 14- does not extend beyond ten such sub-groups. Another cable 15 serves in the same way the line switches of the second group, eight subgroups of which shown. In the same way other cables would serve other groups of line switches.

Each wiper 10 is movable, for automatic trunk selecting purposes, over a series oi contact terminals, one set of which is arbitrarily represented at 16 over the left hand wiper 10 on gheet No. 1. From the bank wires, represented as running thru these cont-acts 16, are taps leading to the wipers 11 repre senting first selectors. Adjacent to each wiper 11 are ten rows of contact points, each row having ten points therein. This ten by ten is arbitrarily represented as three by three at 17, three being considered as representing ten.

The bank wires (trunks) running thru contacts 16 extend different distances, but all are limited to the first one thousand line switches. Those belonging to the second one thousand are multipled to other contact points, one set of which is represented at 18 on Sheet 2. In the same way each thousand line switches has bank wires limited to itself.

Referring to the lower left hand part of Sheet No. 1, it will be seen that the two lower trunks 19 extend over and are limited to the first one hundred line switches in the first group of one thousand. Similarly, the second one hundred line switches have two trunks 19 which are limited to this second one hundred. The third one hundred has two trunks 19", the fourth has two trunks 19. and so on.

Next above the trunks 19 are two other trunks 20 which extend over and are CORP men for two hundred line switches, but are limited. to this two hundred. The next two hundred have the common trunks 20 and so on. Next above the tru ks are live trunks 21 which extend over and are com.- mon for five hundred line switches. The second. five hundred line switches in the first one thousand have similar trunks 21 ll ext above the trunks 21 are ten trunks 22 which extend over the entire one thousand line switches, and are common for the use of the entire number. Each one thousand line switches in the entire exchange has its trunks arranged in the same way.

Assuming that the first line switch represented at the lower left hand corner of Sheet No. 1 is started into operation, it will first engage terminals of trunks which do not extend beyond the sub-group of one hundred line switches to which it belongs. H both of those are busy at the tree, it will pass on to the terminals of trunks common to two hundred line switches. it those are busy, it will pass on to trunks common to five hundred line switches. If those also are busy, it will pass on to trunks common. to the entire thousand.

It will be seen from the foregoing that there are fi'jty trunks serving the first one thousand line switches, yet no line switch finds it necessary to traverse more than nineteen terminals to have the run benefit of the five per cent trunking. The principle here involved makes small number of trunks (preferably two or three) common for a sub-group, another small number common for two or more sub-groups, another number common for a greater number of subgroups, id still another number (preterably large) common for the entire group. The inunbers given (two, two, five, nd ten, yielding a total of nineteen) convenient, but it will be obvious that there may be a variation of the number of trunlrs in each stage, and even varia ion in the number of stages, without departing from the principles involved. Either out these variations may vary the total number of trunks without change of principle.

[is tar as making the final connection to a wanted subscriber, it does not make any dillerence which one of these nineteen trunks the line switch finds idle. For example, it will. be assumed that the subscriber whose line switch is represented at the lower left hand corner of Sheet No. 1 wants to make connection to some other subscriber in the same thousand. It he finds either of the trunks 19 idle he gets one of the two selectors 11 at the extreme left as is indicated by the tap wires leading from the trunks 19. l Vanting a subscrioer in the fii ten thousand, the calling subscriber starts his switch 11 moving along the Pet row of contact points which connects him to an idle trunk in cable 23 and gives him an idle switch 12 in the group of ten at the extreme left. [is the bank contacts of these switches are multipled together in ordinary manner, it does not make any dilierence whi one i gets. Having thus got possessio of a switch 12, and wantii some connccdon in the first thousand, he

ers up the first row or contacts and secures some idle trunk in the cable 24. This gives him an idle connector 13 in the group of? ten at the extreme left. it the wanted subscriber is in the first hundred. the connector 13 is advanced along the first row of contacts to the correct number. if the want- ....arts his switch wiptrn naeaeei ed subscriber is in the second hundred, the connector is moved laterally to the second row, and then advanced. And so on.

If the line switch, instead of connecting to a trunk 19 as just described, should not find an idle trunk until it reached the last one of the trunks 22 it would come to switch 25 shown near the middle of Sheet No. 2. This switch, like all of those in its immediate neighborhood, would have its contacts multipled to the same bank wires as those shown for the adjacent wiper 11. Moving up the first row of contacts (as in case previously described) the selector would find an idle trunk in cable 26 leading to one of the second selectors C in the fifth sub-group of such selectors shown in the middle of Sheet No. 2. Again moving up the first row of contacts the second selector would find an idle trunk in cable 27 leading to a connector D in the fifth sub-group. All of the connectors in the five sub-groups their contact points multipled to the wires in cable 14:, and hence the connection to the desired subscriber would be the same as that before described.

It will be observed that the drawings show connectors, all of which have their contacts multipled to the Wires in cable 1% leading to the one thousand subscribers represented by tiieir wipers 10 in the first main group. Hence, any one of the fifty connectors may be used to complots the connection to a called subscriber. Also it is to be observed that between the line switches and the connectors there fifty first selectors and fifty second selectors any one of which may be used in completing connections. ln the manner just described, the trunking connections may be traced on the drawing from any line switch in the first thousand to any other'line switch in the same thousand. Hence the drawings illustrate five per cent trunking in groups of one thousand without large or unusual. switches at any point except the connectors. it will be obvious that by'inserting third selectors the same plan can be carried out with ordinary connectors without other change.

The cable 2 l- (leading to the first, subgroup of connectors in th first thousand) extends thru the exchange and may be traced on Sheets Nos. 2 and 3. Hence, this cable may be reached by connections from the line sv'tches in any other thousand. Thus, if the first line switch in the second thousand (shown adjacent to the vertical part of cable 15 on Sheet No. 2) should get the first selector directly over it and this L: ..-L QQTIUL 11. 1, -1 MB 31% nice color. L01. 5 -oinc at Valid, on it led low, it would come to cable 28, and thence thru a second selector to cable 2d. Similarly,

2" a l "l t 1 d t bl c.u.-e z, anc otier lIlcEllllQ 1a c ca es, .i tend thru the exchange and may be reached,

thru first and second selectors, by any line switch in any thousand.

4f the subscriber having the first selector in the first thousand wanted to call some person in the second thousand, he would proceed as before up to the second selector 12. Then, instead of advancing up the first row of contacts he would shift his wiper to the second row and then advance up that row. This would make connection to an idle trunk in cable 29, which ext-ends into the second thousand and has a branch 30 leading to the connectors shown in the upper right han corner of Sheet No. 2. if the person wanted is in the third thousand, then the second selector 12 would be shift ed to and advz-iuced on the third row of contacts. This would give a trunk in cable 31 leading to connectors in the third group of one thousand. ln the same way sh fting the second selector to the third, fourth, fifth or later row of contacts would carry the connections to the third, fourth, li -th or later thousand in the first ten thousan if the subscriber to be called is in the second ten thousand, then, in making a call, the first selector ii is shifted to the second row and secures an idle trunk in the cable 32. This cable is united with other cables to form a large cable extending to the eleventh thousand, twenty-first thousand, thirty-first thousand, etc. The particular cable 32- would have taps emerging from cable 33 at the eleventh thousand and would give a second selector in the same way that a second selector was secured from cable 23 in the previous description. Having found a second selector in the second ten thousand, this selector can be advanced on any row of contacts to get a connector in any thousand, in the same manner as described for the first ten thousand. if the subscriber to be called is in the third ten thousand, then the calling subscriber moves his first selector to the third row and gets a trunk in cable 34 whichunites with cable 33 and later emerges at the twenty-first thousand. And so on.

The switches and trunks shown on Sheets Nos. 2 and 3 belong in the second one thousand and correspond exactly to those de-- scribed as being in the first one thousand. The cables reached by the first selectors are gathered in the same way into a large cable like 33, and later emerge at the twelfth, the twenty-second, and thirtysecond, etc, thousand. The same arrangement carried out in the same way extends to the other parts of the exchange.

In ordinary exchanges using groups of one hundred subscribers, ten per cent of trunking meets the ordinary runs of calls. T he reason why approximately fourteen per cent of trunking is necessary in such ere changes is that occasionally there is a con- 4 rec gestion of calls from soni cular hundred, and unless there p for meeting such congcs ion t 0. calls is cone eater c b s down as far as meetin. cerned. The smaller th m (lo liability.

In my arrangement divj into groups of one thou. vide these into subhundred, the l m) any other percentag five per cent. That is or to meet any kind of congestion, becaus gestions oi tralfic are usually local.

Passing beyond the line switch be seen that l have arranged t over each other in sub-groups of any first selector is being m I called subscriber in the fir. it moves up the row oi I 7 gives it connection to one or": second selectors. Going to the second row would carry the connections oil into the second ten thousand. A first selector is able to seize only one or the ten trunks leading to a corresponding sub-group of second selectors, and similarly, an advancing second selector is able to seize only one or the ten trunks leading to connectors.

To casual inspection it might seem this provided. five per cent trun groups, and that a congestion or ca= center on the first and second s Such, however, is not the fact can he mace evident by returning to the trunking arrangement from the line switches to the first selectors.

The first selectors of the first thousand are ar "anged in ten groups of five in each group, the entire fifty serving one thousand subscribers. Each line switch has access to nineteen of the fifty first selectors, but this access is distributed thru different parts of the fifty, and not concentrated at one place. The first one hundred line switches have access to eight first selectors of the first group 01" ten; to tour of the second worm; and to two of the fifth group. The other line switches of each hundred have their trunk connections similarly distributed over the difi erent groups 01" first selectors. Consequently it will be seen that a congestion of calls originating in any hundred line switches has those calls distributed to difierent groups of selectors and not concentrated in any one group. And a distribution which reaches the first selectors is continued in the same way to the second selectors and to the. connectors.

If it is desired to increase the selectorsv m ihis would give cw nty-one Contact points each line Also, the same reinserting five l or by inserting ten extra bani; Wli" i any one of these additions the percentage uniting may be i seven per cent for extremely husy sections.

In exchanges in which the trafiic is light ur per cent trunking in .r. be that ips of one thousand will care for every contingency In such cases the desired reduction may be obtained by the reverse iccss to that just described. Thus, omitting one of the wires 19-, 19 etc, will leave only forty selectors to one thousand trunks. Similarly, omitting the two trunks 20, 20*, etc, or the five trunks 21 and 21 will each accomplish the same result. Either oi these last two, however, will cut out one of the stapes by wnich congested calls are dis tributed thru ditl'erent parts of the apparatus.

From the foregoing description it will be seen that E have set forth a system of distributing congested calls thru difi erent p rts oi the exchange so that the percentage of trunl-Iing may be lar ely reduced from what is now necessary to meet the requirements of a given traffic. Also, that l accomplish these results by the use of the same apparatus now commonly employed. Also, that the system described is extremely flexible and may be adapted to widely varying condilOIlS.

Vlhat I claim is:

1. In an automatic telephone exchange, a series of line switches divided, into groups, a series of selectors divided into corresponding groups, and a series of trunk connections between the line switches and the selectors, said trunk connections being divided into classes which do not correspond to said groups but which permit any line switch to automatically complete direct connections to some idle selector in any group of selectors.

2. In an automatic telephone exchange, a series of line switches each having contact terminals thereon, a series of selectors more numerous than the terminals on any line switch, said selectors being divided into groups less numerous than the terminals on a line switch, and trunks connecting each selector to terminals on a plurality of can line switches, said trunks being divided into classes which diilter from the groups and are determined b the number of line switches to whose terminals they are multipled.

3. In an automatic telephone exchange, a series 01" line switches divided into groups,

o 31. trunk connections selectors to or ors also divided into groups, extending from the tact terminals on the line switches, said runl: connections being dividcd into classes part of which classes connect a plurality of groups of selectors to a plurality of groups of line switches.

4t. automatic telephone exchange, a series Oil line switches each having a pin" rality of contact terminals, a series of selectors more numerous than the contact terminals on a line switch and divided into groups less ninoerous than such terminals, means by which upon o erating a line switch it will automatically select both group and selector so as to complete connections to an idle selector in some group having such idle selector, and other electrical connections by which final telephonic connection reaches the same place without respect to which group is thus automatically selector.

5. ln automatic telephone exchanges, the combination with line switches divided into groups, and a lesser number of selectors divided into corresponding groups, or" direct trunk connections between line switches and selectors, said connections being so arranged that calls coming thru line switches will be sent normally to the selectors of corresponding groups, but upon a congestion of calls coming thru any particular group of line switches the surplus of such calls will be distributed to selectors of other groups over said connections.

6. The combination with line switches divided into groups, and a lesser number of selectors divided into corresponding groups, of trunk connections from line switches to selectors so arranged that upon a congestion of calls coming thru any group of line switches all calls beyond a certain number will be distributed to different groups of selectors, and means by which a call finally reaches the same place without respect to what group of selectors it passes thru.

7. In a telephone system, a series of subscribers individual line switches divided into groups, a series o1 selectors divided into corresponding groups, a series of trunk connections between said individual switches L said trunlr connections selectors, each third choice trunk line being common to a plurality of line switch groups and individual to one group of selectors,

and said trunk lines permitting any line switch to connect with a selector in any group of selectors.

9. In a telephone system, line switches divided into groups, selector switches divide ed into corresoonding number of groups, first choice trunk lines accessible to only one group of line switches and terminating in selector switches of only one group, sec ond choice trunlr lines accessible to two groups oi line switches and terminating in selector switches of only one group, third choice trunk lines accessible to a plurality of, groups of line switches and terminating in a plurality 01 groups of selector switches, and said trunk lines permitting any line switch to connect with a selector switch in any group of selector switches.

10. In a telephone system, a series of subscribers individual line switches divided into groups, a series of selectors divided into corresponding number of groups, trunk lines connecting said line switches and said selectors, certain of said selectors being accessible to only one of said line switch groups, other of said selectors accessible to only two of said line switch groups, still other of said selectors being accessible to all of said line switch groups, and the trunk connections between said last mentioned selectors and line switches arranged so that any line switch in any group of line switches can select an idle selector in any group of selectors.

FRANK A. LUNDQUIST. 

